FIG. 24 shows an example of a rechargeable battery, which is one type of a power storage device. The rechargeable battery includes an electrode assembly 84 formed by spirally winding a strip of positive electrode 81, a strip of negative electrode 82, and a strip of separator 83 arranged between the electrodes 81 and 82. Specifically, the positive electrode 81 includes an active material layer 81a, to which an active material is applied, and non-application portions 81b (collection portions), to which an active material is not applied. In addition, the negative electrode 82 includes an active material layer 82a, to which an active material is applied, and non-application portions (collection portion), to which an active material is not applied. In FIG. 24, the non-application portions of the negative electrode 82 are not shown.
The positive electrode 81 and the negative electrode 82 are stacked with the separator 83 arranged in between and spirally wound with the non-application portions 81b of the positive electrode 81 and the non-application portions of the negative electrode 82 extending outward from opposite sides of the separator 83. After the positive electrodes 81, the negative electrodes 82, and the separators 83 are spirally wound, the positive electrode 81, the negative electrode 82, and the separator 83 are pressed from opposite sides in the radial directions. This forms a flat electrode assembly 84. Then, the electrode assembly 84 is placed in a case 80a, which is filled with an electrolyte, to form a rechargeable battery 80 (see Patent Document 1, for example).
The electrode assembly 84 includes a power collection group 81c, which is formed by gathering the non-application portions 81b of the positive electrode 81. The power collection group 81c extends perpendicular to the stacking direction of the electrode assembly 84. A planar collector 85 is connected to a surface of the power collection group 81c that is perpendicular to the stacking direction of the electrode assembly 84. The collector 85 is electrically connected to the positive electrode 81 by performing ultrasonic welding to join the portion where the collector 85 and the power collection group 81c are in contact. The negative electrode 82 is electrically connected to a collector (not shown) in the manner as the electric connection of the positive electrode 81 and the collector 85.